Much of the effort of the art in the past in crown control has been directed to bending the work rolls or backup rolls to exert pressure on the center of the work surface. Bending of large rolls operating at high speed is difficult and requires massive machinery. Arbors and bendable rolls may be equipped with a sleeve as disclosed by Ginzburg in U.S. Pat. Nos. 4,813,258, 5,093,974 and 5,347,837. An early sleeve on a mandrel is shown by Fawell in U.S. Pat. No. 1,864,299. Frank, in U.S. Pat. No. 1,919,158, also shows an early "rigid beam" having a "heavy shell" and bearings between and around the beam; see also Wood U.S. Pat. No. 2,010,211. Various hydraulic systems have been used to flex a sleeve, either directly or indirectly, mounted on an arbor or other type of back-up device--see Bretschneider, U.S. Pat. No. 3,604,086, Lehman U.S. Pat. No. 3,879,827, Takigawa et al U.S. Pat. No. 4,242,781, Eibe U.S. Pat. No. 4,062,096, Biondetti U.S. Pat. No. 3,949,455, and Christ U.S. Pat. No. 4,059,976 (see FIG. 3 particularly).
Others have developed more direct mechanical methods of reinforcing the center of the work roll. See Gronbeck's hollow back-up roll which may be supported by discs (U.S. Pat. No. 4,407,151), the variable shaped back-up roll of Yoshii et al in U.S. Pat. No. 4,596,130, the variably controlled thrust load application devices of Matricon et al in U.S. Pat. No. 4,912,956 and Dominique in U.S. Pat. No. 4,882,922, and the fixed supports Guettinger describes in U.S. Pat. No. 4,414,889. Schnyder's hydrostatic support elements have bearing surfaces on inner traveling ring surfaces "deformed into a slightly elliptical shape"--col. 4, line 67. Ellis, in U.S. Pat. No. 4,676,085, controls the positions of hydraulic piston cylinder assemblies which act on an intermediate roll 24.
In U.S. Pat. No. 4,875,261, Nishida discusses prior art in which a back-up roll is equipped with cylindrical rollers between the roll shaft and an outer casing. He adds tapered roller bearings between the cylindrical rollers and an outer casing to receive a thrust load from the cylindrical rollers.
Negative and positive crowns are created by Verbickas according to U.S. Pat. No. 4,156,359, which shows eccentric cluster rolls in FIG. 2. The eccentric cluster rolls may be turned to vary the force on the surface of the working rolls. Masui et al, in U.S. Pat. No. 4,860,416, discloses a "variable crown" configuration employing tapered bearings between an arbor and a sleeve. While the "radial center of the inner peripheral surface of the inner race of each bearing is eccentric with respect to the radial center of outer peripheral surface of the inner race of the same bearing at the ends of the inner races" ('416 col 5 lines 21-25), this condition (see FIG. 16 of '416) is symmetrical around the entire bearing, i.e. there is no eccentricity or variation in the distance from the axis of the arbor to the outside of bearings. Tomizawa et al U.S. Pat. No. 5,007,152 is based on Masui and employs a curved arbor to vary the crown profile.
The art is still searching for a simple crown control system that can be operated using a single back-up roll.